Probably, but he'd be wrong to do so.

Without breaking any storylines for those who haven't started the book yet, one of the new main characters is a former boxer who beat up the guys who assaulted Bonasera's daughter (in the original novel). Puzo had written that Clemenza had taken care of all the details on that job, yet Winegardner has this character as part of Tessio's crew.

BTW - Its apparent that Winegardner is following the original novel only and not the movie (ie. the ages of the Corleone sons..... Tom Hagen, for example being born in 1910, and not in 1916 as was suggested by the movie).